Copter: support logging while disarmed
Copter: remove extra in_mavlink_delay from should_log function

Also return false when logging disabled
Copter: add NearlyAll-AC315 LOG_BITMASK description
AP_Compass: added set_offsets() interface

this will be used by Replay to prevent the need for saving parameters
Replay: fixed loading of users parameters and parameter override

use compass.set_offsets() to avoid trying to write to storage